SocialPub/PrivaPub/Federation/Actors/ActorDocument.cs

using System.Text.Json;

using PrivaPub.Federation.Objects;

namespace PrivaPub.Federation.Actors
{
	public sealed record ActorKey(string Id, string Pem);

	public sealed class ActorDocument
	{
		static readonly string[] ActorTypes = { "Person", "Service", "Application", "Group", "Organization" };

		public string Id { get; init; }
		public string Type { get; init; }
		public string PreferredUsername { get; init; }
		public string Name { get; init; }
		public string Summary { get; init; }
		public string Url { get; init; }
		public string Inbox { get; init; }
		public string Outbox { get; init; }
		public string Followers { get; init; }
		public string Following { get; init; }
		public string SharedInbox { get; init; }
		public string Icon { get; init; }
		public bool Discoverable { get; init; } = true;
		public IReadOnlyList<ActorKey> Keys { get; init; } = Array.Empty<ActorKey>();

		public ActorKey Key(string keyId) => Keys.FirstOrDefault(k => k.Id == keyId);

		public static ActorDocument Parse(JsonElement root)
		{
			if (root.ValueKind != JsonValueKind.Object)
				return default;
			var id = RemoteActorService.Text(root, "id");
			var type = RemoteActorService.Text(root, "type");
			if (Origin.Of(id) == default || !ActorTypes.Contains(type))
				return default;

			var inbox = RemoteActorService.Text(root, "inbox");
			return new ActorDocument
			{
				Id = id,
				Type = type,
				PreferredUsername = RemoteActorService.Text(root, "preferredUsername"),
				Name = RemoteActorService.Text(root, "name"),
				Summary = RemoteActorService.Text(root, "summary"),
				Url = RemoteActorService.Text(root, "url") ?? id,
				Inbox = Origin.Same(inbox, id) ? inbox : default,
				Outbox = RemoteActorService.Text(root, "outbox"),
				Followers = RemoteActorService.Text(root, "followers"),
				Following = RemoteActorService.Text(root, "following"),
				SharedInbox = root.TryGetProperty("endpoints", out var endpoints) ? RemoteActorService.Text(endpoints, "sharedInbox") : default,
				Icon = root.TryGetProperty("icon", out var icon) ? RemoteActorService.Text(icon, "url") : default,
				Discoverable = !root.TryGetProperty("discoverable", out var discoverable) || discoverable.ValueKind != JsonValueKind.False,
				Keys = ParseKeys(root, id)
			};
		}

		static List<ActorKey> ParseKeys(JsonElement root, string actorId)
		{
			var keys = new List<ActorKey>();
			if (!root.TryGetProperty("publicKey", out var publicKey))
				return keys;
			var candidates = publicKey.ValueKind switch
			{
				JsonValueKind.Object => new[] { publicKey },
				JsonValueKind.Array => publicKey.EnumerateArray().Where(k => k.ValueKind == JsonValueKind.Object).ToArray(),
				_ => Array.Empty<JsonElement>()
			};
			foreach (var key in candidates)
			{
				var keyId = RemoteActorService.Text(key, "id");
				var owner = RemoteActorService.Text(key, "owner");
				var pem = RemoteActorService.Text(key, "publicKeyPem");
				if (string.IsNullOrEmpty(pem) || owner != actorId || !Origin.Same(keyId, actorId))
					continue;
				keys.Add(new ActorKey(keyId, pem));
			}
			return keys;
		}
	}
}